As a conventional technique of the present invention, Patent Document 1 describes “a X-ray diffraction device and a position sensitive gas-filled X-ray counter”, for example.
FIG. 2 schematically illustrates the above-stated conventional X-ray diffraction device. Reference numeral 4 denotes a measurement chamber of a high vacuum atmosphere, inside of which a position sensitive gas-filled X-ray counter 5 is provided. Reference numeral 2 denotes a specimen. Incident X-ray 1 is incident to the specimen 2 in the direction of the arrow. The direction of diffracted X-ray 3 will be varied depending on the specimen, and when the specimen is a polycrystal, for example, the X-rays will be diffracted in a plurality of directions concurrently as illustrated in FIG. 2. The plurality of diffracted X-rays 3 is counted concurrently by the position sensitive X-ray counter 5.
The position sensitive X-ray counter 5 includes double-layered X-ray transmission windows 6 and 7 opposed to each other with a predetermined gap (e.g., 10 mm) therebetween, each having an arc shape (e.g., extending at the angle of)120° centered about a measurement position of the specimen, where an inside of the inner X-ray transmission window 7 (a first window) is called a counter portion 11, and an inside of the outer X-ray transmission window 6 (a second window) is called a vacuum vessel portion 10. The X-ray transmission window 6 is made of a high-polymer organic film of 2.5 μm in thickness, and the X-ray transmission window 7 is made of a beryllium film of 7.5 μm in thickness. An operation gas is filled in the counter portion 11, and electrodes 8 and 9 are disposed therein.
Reference numeral 22 denotes a plurality of gas cylinders, from which a plurality of gases are introduced to a gas mixer 21 via decompression valves to set the composition of gas. Reference numeral 18 denotes a pressure regulator including a pressure indicator, a variable leak valve and a controller not illustrated. In accordance with a difference between a preset pressure and a measurement pressure by the pressure indicator not illustrated, the controller performs PID (proportional-plus-integral-plus-derivative) control to open/close a variable leak valve 19 so as to regulate conductance, thus supplying the operation gas to the counter portion 11 while keeping a gas pressure constant. Reference numeral 20 denotes a rotary pump. The pressure can be controlled by regulating the variable leak valve 19 and a gain and a time constant of the controller in the pressure regulator 18. That is, the operation gas composition and the pressure control (regulating) mechanism are used so as to adjust the counter efficiency of the X-ray counter and the X-ray transmittance to be optimal values in accordance with the energy of the X-ray measured.
The vacuum vessel portion 10 is evacuated by a turbo molecular pump 14 and a rotary pump 15. Reference numeral 16 denotes a vacuum gage, based on which if the pressure of the vacuum vessel portion 10 is higher than a preset threshold because of breakage of the X-ray transmission window 7, a closing valve 17 is closed automatically, thus preventing leakage of the operation gas to the measurement chamber 4 of a high vacuum atmosphere.
When air is to be leaked to the counter portion 11, the vacuum vessel portion 10, or the measurement chamber 4 of a high vacuum atmosphere, the leaking has to be conducted while keeping the pressures of the counter portion 11, the vacuum vessel portion 10 and the measurement chamber 4 equal so as to prevent the breakage of the X-ray transmission windows 6 and 7. To this end, the valve 17 is firstly closed to shut off the supply of the operation gas and reduce the pressure of the counter portion, followed by opening of the valves 23, 24, and 25 to make the pressures of the portions 11, 10 and 4 equal, and then the leak valve 26 is opened so as to introduce dry air passing through an air drier 27. In this operation, in order to minimize a differential pressure applied to the X-ray transmission windows 6 and 7, attention has to be paid so as to make conductance from the leak valve 26 to both surfaces of the X-ray transmission windows 6 and 7 equal.    Patent Document 1: JP Published Patent Application No. 05-332958 A (1993)